Multiplex telegraph system with magnitude discrimination



Jan. 18; 1927.. 614,555

H. V. HUNTER MULTIPLEX TELEGRAPH SYSTEM WITH MAGNITUDE DISCRIMINATIONFiled Dec. 20. 1924 l g 1.9 2 L g 25 E F aw L 1 g 2 l I I! I .4 1 II I ll I: l .4 v

X Z INVENTOR 11%.; iZT fflzntei' ATTORNEY Patented Jam 18,1927.

nowenn v. HUNTER, on NEW YORK, n.

Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATIONOF NEW YORK.

MULTIPLEXITELEGRAZPH SYSTEM WITH MAGNITUDE DISCRIMINATION.

Application filed December 20, 1924. Serial No. 757,237.

An object of my invention is to provide a new and improved systemf..multiplex telegraphy, in which the discrimination between messagesbelonging to two different message channels is eflected bydiscrimination of the magnitude of the corresponding signal currents.Another object of my invention is to provide for magnitudediscrimination by utilizing vacuum tube rectifiers of differentcharacteristics. These and other objects of my invention will becomeapparent on consideration of a specific example which I havechosen to bedescribed in the following specification. With the understanding that,the description here given applies to this particular embodiment ofthe'invention, the invention will be defined in the appended claims. a

Referring to the drawings, Figure 1 is a diagram of the sending end ofmy transmission system; Fi 2 is a diagram of the receiving end; an Fig.3 is a diagram of the characteristics of vacuum tubes'employed at thereceiving end. q)

The carrier current generator" 26 applies a corresponding electromotiveforce to 'the grid of the three-electrode vacuum tube amplifier 27. Asshown in Fig, 1, the grid 1s shunted through the closed armature con- 0tacts 19 and 20. The sending key 21 operates when closed to open thecontact 19 and interpose the resistance 23, 25 in the shunt referred to,so that a corresponding magnitude of electromotive force is then ap- 5plied to the grid. Onthe other hand, the closure of the key 22 opens thecontacts at and interposes the resistance 24, 25 and puts a greatermagnitude of electromotive force on the grid. Simultaneous closing of 3the keys. 21 and 22 puts an electromotive force on the gridcorresponding to the sum of the two electromotive forces determined bythe keys 21 and 22 separately. The output current from the amplifier 27goes through the band filter F tothe bus-bars 28 and thence over theline 29' to the receiving station bus-bars 30. The band filter F"corresponding to the filter F receives the carrier current'viave trains.of corresponding frequency and applies them to the amplifier A andthence to the rectifiers R and R These rectifier have acteristics'shown' in Fig. 3. The rectifier R is designed and adjusted so thatthecurthe volt-ampere ch'arrent starts upfrom zero only after a substantialelectromotive force is applied and \after an abrupt rise it turnsquickly to aconstant value as indicated by tho nearly characteristic 1.In the other rectifier R,

r of Fig. 2, the current increases more nearly uniformly from zeroallthe way, as shown by the characteristic 2. The two voltage is OZ.

The relay 32 in the ohwut circuit of rectifier R and the relay 31hasdilferential wmdings in the output circuits of both rectifiers R andR The relay 32 controls the sounder, 34, and the relay controls thesounder 33.

-When key- 21 only is-closed, the voltage gives an out ut current XAfrom rectifier R, and X from'rectifier R The current XA is too small toactuate the relay 32 but the current XA'? is so much greater than XAthat there is a substantial differential effect in the relay 31 and itoperates the circuit of the sounder 33. I On theother hand,-when the key22 alone is closed, the electromotiveforce OY gives the same outp tcurrent for the two rectifiers R and as represented by the ordinate YB.This current is of suiiicient mag nitude to operate the relay 32 and itsasso ciated sounder. 34 but in the relay 31 the effect neutralizes orbalances out-so that there is no operation of the sounder 33.

When both keys 21 and 22 are closedv simultaneously, the electromotiveforce OZ produces respective currents ZC in the output circuit ofrectifier R and ZC in the output circuit of rectifier R The current ZC"actuates the relay 32 and the differential current Q/C operates therelay 31, so that both sounders 34 and 33 are operated.

. Thus it will be seen that key 21 controls sounder 33 and key 22controls sounder 34 eachindependently of the other.

' I claim:

1. The method of discriminating between signal currents by theirmagnitude effect, which consists in applying themsimnltmwcharacteris- Ihas touch at the value correspondmg to inously to a plurality of vacuumtubes of different shaped characteristics and getting the differentialeffect'of the output currents from those tubes.

2. In a multiplex signaling system, means to send superposed signalcurrents? of different intensity for different message channels twovacuum tubes of different characteristics to which the said currents areapplied, and a differential relay with windings to receive the outputcurrents from both tubes. 5 l

3. The method of discriminating between two signal currents by theirmagnitude cff'ect, which consists in applying them simultaneously toeach of' two vacuum tubes with characteristics as shown in Fig. 3, andgetting the difierential efiect of the output currents from those tubes.

4. In a multiplex signaling system, means to send superposed signalcurrents of diff'erent intensity for different message channels, twovacuum tubes having characteristics of different degrees of curvatureand tangent at an intermediate point, a relay in the output circuit ofone tube and another relay having differential windings in the outputcircuits "of both tubes. Y

5. The method of discriminating between signal currents by theirmagnitude effect whether such currents are separate or superposed, whichconsists in applying them to two vacuum tubes of different shapedcharacteristics and getting the differential efl'ect of the outputcurrents from the tubes for one message channel, and getting the directeffect of' the output current from one of the tubes for another messagechannel. 7

6. In a multiplex signaling system, means to send superposed signalcurrents of different intensity for different message channels, twovacuum tubes of different char acteristics to which the said currentsare applied, a differential relay with windings to receive the outputcurrents from both tubes, and another relay to receive the outputcurrent from only one of the said tubes.

In testimony whereof, I have signed my name tothis specification this15th day of December, 1924. i I

HOWARD v. HUNTER.

